A wide variety of needle tree injectors are known in the art. Examples of such injectors include those described in U.S. Pat. No. 5,599,302 issued to Lilley et al., U.S. Pat. No. 5,062,830 to Dunlap, and U.S. Pat. No. 4,790,824 to Morrow et al. In general, these and similar injectors administer medication as a fine, high velocity jet delivered under sufficient pressure to enable the jet to pass through the skin.
Although these injectors are quite successful from a technical point-of-view in achieving the desired delivery of medicament, most commercially available needle tree injectors have practical limitations. For example, most needle free injectors are bulky in size. In addition to the undesirable size, some needle tree injectors require a complex sequence of coupling and uncoupling the injector to a vial containing the medicament. Thus, there is a perception by the user that the injector is difficult to use. Finally, some needle tree injectors cannot be used with standard medicament cartridges, i.e. a cylindrical chamber, typically made of glass, having a first end with a seal penetrable by a needle to draw medicament out of the cartridge and a second end with a movable stopper.
Thus, there exists a need for an improved medical injector and loading system that is compact, usable with standard medicament cartridges, and perceived as easy to operate.